﻿//******************************************************************************************************
//  SrpConstants.cs - Gbtc
//
//  Copyright © 2014, Grid Protection Alliance.  All Rights Reserved.
//
//  Licensed to the Grid Protection Alliance (GPA) under one or more contributor license agreements. See
//  the NOTICE file distributed with this work for additional information regarding copyright ownership.
//  The GPA licenses this file to you under the Eclipse Public License -v 1.0 (the "License"); you may
//  not use this file except in compliance with the License. You may obtain a copy of the License at:
//
//      http://www.opensource.org/licenses/eclipse-1.0.php
//
//  Unless agreed to in writing, the subject software distributed under the License is distributed on an
//  "AS-IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. Refer to the
//  License for the specific language governing permissions and limitations.
//
//  Code Modification History:
//  ----------------------------------------------------------------------------------------------------
//  7/27/2014 - Steven E. Chisholm
//       Generated original version of source code. 
//       
//
//******************************************************************************************************

using System;
using System.Collections.Generic;
using System.ComponentModel;
using Org.BouncyCastle.Crypto.Digests;
using Org.BouncyCastle.Math;

namespace GSF.Security.Authentication
{
    /// <summary>
    /// Supplies the base constants of SRP (Secure Remote Passord) as supplied in RFC 5054 Appendix A.
    /// </summary>
    /// <remarks>
    /// This implementation of SRP uses SHA-512 as the performance difference between 
    /// SHA1 and SHA-512 is negligable.
    /// </remarks>
    internal class SrpConstants
    {
        public BigInteger N;
        public BigInteger g;
        public BigInteger k;
        public byte[] Nb;
        public byte[] gb;
        public byte[] kb;
        /// <summary>
        /// H(N) xor H(g)
        /// </summary>
        public byte[] kb2;

        private SrpConstants(string hexN, string decG)
        {
            N = new BigInteger(hexN, 16);
            Nb = N.ToByteArrayUnsigned();
            g = new BigInteger(decG, 10);
            gb = g.ToByteArrayUnsigned();
            kb = ComputeHash(Nb, gb);
            k = new BigInteger(1, kb);
            kb2 = Xor(ComputeHash(Nb), ComputeHash(gb));
        }

        /// <summary>
        /// Contains the standard N, g, k parameters depending on the bit size
        /// as specified in RFC 5054 Appendix A.
        /// </summary>
        private static Dictionary<int, SrpConstants> s_groupParameters = new Dictionary<int, SrpConstants>();

        static SrpConstants()
        {
            SrpConstants c;
            c = new SrpConstants(
                "EEAF0AB9ADB38DD69C33F80AFA8FC5E86072618775FF3C0B9EA2314C" +
                "9C256576D674DF7496EA81D3383B4813D692C6E0E0D5D8E250B98BE4" +
                "8E495C1D6089DAD15DC7D7B46154D6B6CE8EF4AD69B15D4982559B29" +
                "7BCF1885C529F566660E57EC68EDBC3C05726CC02FD4CBF4976EAA9A" +
                "FD5138FE8376435B9FC61D2FC0EB06E3", "2");
            s_groupParameters.Add(1024, c);

            c = new SrpConstants(
                "9DEF3CAFB939277AB1F12A8617A47BBBDBA51DF499AC4C80BEEEA961" +
                "4B19CC4D5F4F5F556E27CBDE51C6A94BE4607A291558903BA0D0F843" +
                "80B655BB9A22E8DCDF028A7CEC67F0D08134B1C8B97989149B609E0B" +
                "E3BAB63D47548381DBC5B1FC764E3F4B53DD9DA1158BFD3E2B9C8CF5" +
                "6EDF019539349627DB2FD53D24B7C48665772E437D6C7F8CE442734A" +
                "F7CCB7AE837C264AE3A9BEB87F8A2FE9B8B5292E5A021FFF5E91479E" +
                "8CE7A28C2442C6F315180F93499A234DCF76E3FED135F9BB", "2");
            s_groupParameters.Add(1536, c);

            c = new SrpConstants(
                "AC6BDB41324A9A9BF166DE5E1389582FAF72B6651987EE07FC319294" +
                "3DB56050A37329CBB4A099ED8193E0757767A13DD52312AB4B03310D" +
                "CD7F48A9DA04FD50E8083969EDB767B0CF6095179A163AB3661A05FB" +
                "D5FAAAE82918A9962F0B93B855F97993EC975EEAA80D740ADBF4FF74" +
                "7359D041D5C33EA71D281E446B14773BCA97B43A23FB801676BD207A" +
                "436C6481F1D2B9078717461A5B9D32E688F87748544523B524B0D57D" +
                "5EA77A2775D2ECFA032CFBDBF52FB3786160279004E57AE6AF874E73" +
                "03CE53299CCC041C7BC308D82A5698F3A8D0C38271AE35F8E9DBFBB6" +
                "94B5C803D89F7AE435DE236D525F54759B65E372FCD68EF20FA7111F" +
                "9E4AFF73", "2");
            s_groupParameters.Add(2048, c);

            c = new SrpConstants(
                "FFFFFFFFFFFFFFFFC90FDAA22168C234C4C6628B80DC1CD129024E08" +
                "8A67CC74020BBEA63B139B22514A08798E3404DDEF9519B3CD3A431B" +
                "302B0A6DF25F14374FE1356D6D51C245E485B576625E7EC6F44C42E9" +
                "A637ED6B0BFF5CB6F406B7EDEE386BFB5A899FA5AE9F24117C4B1FE6" +
                "49286651ECE45B3DC2007CB8A163BF0598DA48361C55D39A69163FA8" +
                "FD24CF5F83655D23DCA3AD961C62F356208552BB9ED529077096966D" +
                "670C354E4ABC9804F1746C08CA18217C32905E462E36CE3BE39E772C" +
                "180E86039B2783A2EC07A28FB5C55DF06F4C52C9DE2BCBF695581718" +
                "3995497CEA956AE515D2261898FA051015728E5A8AAAC42DAD33170D" +
                "04507A33A85521ABDF1CBA64ECFB850458DBEF0A8AEA71575D060C7D" +
                "B3970F85A6E1E4C7ABF5AE8CDB0933D71E8C94E04A25619DCEE3D226" +
                "1AD2EE6BF12FFA06D98A0864D87602733EC86A64521F2B18177B200C" +
                "BBE117577A615D6C770988C0BAD946E208E24FA074E5AB3143DB5BFC" +
                "E0FD108E4B82D120A93AD2CAFFFFFFFFFFFFFFFF", "5");
            s_groupParameters.Add(3072, c);

            c = new SrpConstants(
                "FFFFFFFFFFFFFFFFC90FDAA22168C234C4C6628B80DC1CD129024E08" +
                "8A67CC74020BBEA63B139B22514A08798E3404DDEF9519B3CD3A431B" +
                "302B0A6DF25F14374FE1356D6D51C245E485B576625E7EC6F44C42E9" +
                "A637ED6B0BFF5CB6F406B7EDEE386BFB5A899FA5AE9F24117C4B1FE6" +
                "49286651ECE45B3DC2007CB8A163BF0598DA48361C55D39A69163FA8" +
                "FD24CF5F83655D23DCA3AD961C62F356208552BB9ED529077096966D" +
                "670C354E4ABC9804F1746C08CA18217C32905E462E36CE3BE39E772C" +
                "180E86039B2783A2EC07A28FB5C55DF06F4C52C9DE2BCBF695581718" +
                "3995497CEA956AE515D2261898FA051015728E5A8AAAC42DAD33170D" +
                "04507A33A85521ABDF1CBA64ECFB850458DBEF0A8AEA71575D060C7D" +
                "B3970F85A6E1E4C7ABF5AE8CDB0933D71E8C94E04A25619DCEE3D226" +
                "1AD2EE6BF12FFA06D98A0864D87602733EC86A64521F2B18177B200C" +
                "BBE117577A615D6C770988C0BAD946E208E24FA074E5AB3143DB5BFC" +
                "E0FD108E4B82D120A92108011A723C12A787E6D788719A10BDBA5B26" +
                "99C327186AF4E23C1A946834B6150BDA2583E9CA2AD44CE8DBBBC2DB" +
                "04DE8EF92E8EFC141FBECAA6287C59474E6BC05D99B2964FA090C3A2" +
                "233BA186515BE7ED1F612970CEE2D7AFB81BDD762170481CD0069127" +
                "D5B05AA993B4EA988D8FDDC186FFB7DC90A6C08F4DF435C934063199" +
                "FFFFFFFFFFFFFFFF", "5");
            s_groupParameters.Add(4096, c);

            c = new SrpConstants(
                "FFFFFFFFFFFFFFFFC90FDAA22168C234C4C6628B80DC1CD129024E08" +
                "8A67CC74020BBEA63B139B22514A08798E3404DDEF9519B3CD3A431B" +
                "302B0A6DF25F14374FE1356D6D51C245E485B576625E7EC6F44C42E9" +
                "A637ED6B0BFF5CB6F406B7EDEE386BFB5A899FA5AE9F24117C4B1FE6" +
                "49286651ECE45B3DC2007CB8A163BF0598DA48361C55D39A69163FA8" +
                "FD24CF5F83655D23DCA3AD961C62F356208552BB9ED529077096966D" +
                "670C354E4ABC9804F1746C08CA18217C32905E462E36CE3BE39E772C" +
                "180E86039B2783A2EC07A28FB5C55DF06F4C52C9DE2BCBF695581718" +
                "3995497CEA956AE515D2261898FA051015728E5A8AAAC42DAD33170D" +
                "04507A33A85521ABDF1CBA64ECFB850458DBEF0A8AEA71575D060C7D" +
                "B3970F85A6E1E4C7ABF5AE8CDB0933D71E8C94E04A25619DCEE3D226" +
                "1AD2EE6BF12FFA06D98A0864D87602733EC86A64521F2B18177B200C" +
                "BBE117577A615D6C770988C0BAD946E208E24FA074E5AB3143DB5BFC" +
                "E0FD108E4B82D120A92108011A723C12A787E6D788719A10BDBA5B26" +
                "99C327186AF4E23C1A946834B6150BDA2583E9CA2AD44CE8DBBBC2DB" +
                "04DE8EF92E8EFC141FBECAA6287C59474E6BC05D99B2964FA090C3A2" +
                "233BA186515BE7ED1F612970CEE2D7AFB81BDD762170481CD0069127" +
                "D5B05AA993B4EA988D8FDDC186FFB7DC90A6C08F4DF435C934028492" +
                "36C3FAB4D27C7026C1D4DCB2602646DEC9751E763DBA37BDF8FF9406" +
                "AD9E530EE5DB382F413001AEB06A53ED9027D831179727B0865A8918" +
                "DA3EDBEBCF9B14ED44CE6CBACED4BB1BDB7F1447E6CC254B33205151" +
                "2BD7AF426FB8F401378CD2BF5983CA01C64B92ECF032EA15D1721D03" +
                "F482D7CE6E74FEF6D55E702F46980C82B5A84031900B1C9E59E7C97F" +
                "BEC7E8F323A97A7E36CC88BE0F1D45B7FF585AC54BD407B22B4154AA" +
                "CC8F6D7EBF48E1D814CC5ED20F8037E0A79715EEF29BE32806A1D58B" +
                "B7C5DA76F550AA3D8A1FBFF0EB19CCB1A313D55CDA56C9EC2EF29632" +
                "387FE8D76E3C0468043E8F663F4860EE12BF2D5B0B7474D6E694F91E" +
                "6DCC4024FFFFFFFFFFFFFFFF", "5");
            s_groupParameters.Add(6144, c);

            c = new SrpConstants(
               "FFFFFFFFFFFFFFFFC90FDAA22168C234C4C6628B80DC1CD129024E08" +
               "8A67CC74020BBEA63B139B22514A08798E3404DDEF9519B3CD3A431B" +
               "302B0A6DF25F14374FE1356D6D51C245E485B576625E7EC6F44C42E9" +
               "A637ED6B0BFF5CB6F406B7EDEE386BFB5A899FA5AE9F24117C4B1FE6" +
               "49286651ECE45B3DC2007CB8A163BF0598DA48361C55D39A69163FA8" +
               "FD24CF5F83655D23DCA3AD961C62F356208552BB9ED529077096966D" +
               "670C354E4ABC9804F1746C08CA18217C32905E462E36CE3BE39E772C" +
               "180E86039B2783A2EC07A28FB5C55DF06F4C52C9DE2BCBF695581718" +
               "3995497CEA956AE515D2261898FA051015728E5A8AAAC42DAD33170D" +
               "04507A33A85521ABDF1CBA64ECFB850458DBEF0A8AEA71575D060C7D" +
               "B3970F85A6E1E4C7ABF5AE8CDB0933D71E8C94E04A25619DCEE3D226" +
               "1AD2EE6BF12FFA06D98A0864D87602733EC86A64521F2B18177B200C" +
               "BBE117577A615D6C770988C0BAD946E208E24FA074E5AB3143DB5BFC" +
               "E0FD108E4B82D120A92108011A723C12A787E6D788719A10BDBA5B26" +
               "99C327186AF4E23C1A946834B6150BDA2583E9CA2AD44CE8DBBBC2DB" +
               "04DE8EF92E8EFC141FBECAA6287C59474E6BC05D99B2964FA090C3A2" +
               "233BA186515BE7ED1F612970CEE2D7AFB81BDD762170481CD0069127" +
               "D5B05AA993B4EA988D8FDDC186FFB7DC90A6C08F4DF435C934028492" +
               "36C3FAB4D27C7026C1D4DCB2602646DEC9751E763DBA37BDF8FF9406" +
               "AD9E530EE5DB382F413001AEB06A53ED9027D831179727B0865A8918" +
               "DA3EDBEBCF9B14ED44CE6CBACED4BB1BDB7F1447E6CC254B33205151" +
               "2BD7AF426FB8F401378CD2BF5983CA01C64B92ECF032EA15D1721D03" +
               "F482D7CE6E74FEF6D55E702F46980C82B5A84031900B1C9E59E7C97F" +
               "BEC7E8F323A97A7E36CC88BE0F1D45B7FF585AC54BD407B22B4154AA" +
               "CC8F6D7EBF48E1D814CC5ED20F8037E0A79715EEF29BE32806A1D58B" +
               "B7C5DA76F550AA3D8A1FBFF0EB19CCB1A313D55CDA56C9EC2EF29632" +
               "387FE8D76E3C0468043E8F663F4860EE12BF2D5B0B7474D6E694F91E" +
               "6DBE115974A3926F12FEE5E438777CB6A932DF8CD8BEC4D073B931BA" +
               "3BC832B68D9DD300741FA7BF8AFC47ED2576F6936BA424663AAB639C" +
               "5AE4F5683423B4742BF1C978238F16CBE39D652DE3FDB8BEFC848AD9" +
               "22222E04A4037C0713EB57A81A23F0C73473FC646CEA306B4BCBC886" +
               "2F8385DDFA9D4B7FA2C087E879683303ED5BDD3A062B3CF5B3A278A6" +
               "6D2A13F83F44F82DDF310EE074AB6A364597E899A0255DC164F31CC5" +
               "0846851DF9AB48195DED7EA1B1D510BD7EE74D73FAF36BC31ECFA268" +
               "359046F4EB879F924009438B481C6CD7889A002ED5EE382BC9190DA6" +
               "FC026E479558E4475677E9AA9E3050E2765694DFC81F56E880B96E71" +
               "60C980DD98EDD3DFFFFFFFFFFFFFFFFF", "19");
            s_groupParameters.Add(8192, c);

        }

        /// <summary>
        /// Looks up the valid precomputed constants for SRP given the specified bit strength.
        /// </summary>
        /// <param name="strength">the bit strength to lookup.</param>
        /// <returns></returns>
        public static SrpConstants Lookup(SrpStrength strength)
        {
            int bits = (int)strength;
            SrpConstants value;
            if (!s_groupParameters.TryGetValue(bits, out value))
                throw new InvalidEnumArgumentException("strength");
            return value;
        }

        /// <summary>
        /// Computes the XOR of the supplied parameters
        /// </summary>
        /// <param name="a"></param>
        /// <param name="b"></param>
        /// <returns></returns>
        private static byte[] Xor(byte[] a, byte[] b)
        {
            if (a.Length != b.Length)
                throw new Exception();
            byte[] rv = new byte[a.Length];
            for (int x = 0; x < a.Length; x++)
            {
                rv[x] = (byte)(a[x] ^ b[x]);
            }
            return rv;
        }

        /// <summary>
        /// Computes the hash of all of the supplied parameters.
        /// </summary>
        /// <param name="words"></param>
        /// <returns></returns>
        private static byte[] ComputeHash(params byte[][] words)
        {
            Sha512Digest hash = new Sha512Digest();
            hash.Reset();
            foreach (var w in words)
            {
                hash.BlockUpdate(w, 0, w.Length);
            }
            byte[] rv = new byte[hash.GetDigestSize()];
            hash.DoFinal(rv, 0);
            return rv;
        }
      
    }
}


